THE PASTEURIZATION OF MILK 



the heaters, into which the milk was allowed to 

 flow from the heaters and in which the hot milk 

 was held for the time required by the regulations. 



As before stated, the forms of heaters in use 

 in 1909 are still employed, with certain new forms 

 made by many different manufacturers. They are 

 all comprised under some one of five typical forms, 

 as follows: 



First Type. The so-called Danish heater is 

 sold by various firms. It is shown in the accom- 

 panying illustrations (Figs. 1 and 2). This is 

 the oldest form of heater in use in this country. 

 In this form a large central cylinder is provided 

 with a double cover or jacket. The space between 

 the inner and outer shell is filled with water, into 

 which steam is introduced. By means of a 

 suitable device the steam is distributed through the 

 water at various points. 



In operation, the milk is allowed to flow or is 

 pumped into the inner compartment or cylinder, 

 and by means of rapidly revolving paddles it is 

 thrown by centrifugal force against the inner sur- 

 face of the cylinder. This surface is kept hot by 

 means of the hot water and steam in the outer 

 shell. The milk enters at the bottom of the cylin- 



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